Standardization works of international mobile telecommunication (IMT)-advanced which is a next generation (i.e., post 3rd generation) mobile communication system are carried out in the international telecommunication union radio communication sector (ITU-R). The IMT-advanced aims at support of an Internet protocol (IP)-based multimedia service with a data transfer rate of 1 Gbps in a stationary or slowly moving state or 100 Mbps in a fast moving state.
3rd generation partnership project (3GPP) is a system standard satisfying requirements of the IMT-advanced, and prepares LTE-advanced which is an improved version of long term evolution (LTE) based on orthogonal frequency division multiple access (OFDMA)/single carrier-frequency division multiple access (SC-FDMA) transmission. The LTE-advanced is one of promising candidates for the IMT-advanced. Technology related to a relay station is one of main technologies for the LTE-advanced.
A relay station (RS) is a device for relaying a signal between a base station (BS) and a user equipment (UE), and is used for cell coverage extension and throughput enhancement of a wireless communication system.
Many researches for a method of transmitting a signal between the BS and the RS are currently ongoing in the wireless communication employing the RS. A conventional method of transmitting a signal between the BS and the UE has a problem when a signal is transmitted between the BS and the RS.
In the conventional method of transmitting the signal between the BS and the UE, the UE transmits the signal through one entire subframe in a time domain. One reason of transmitting a signal by the UE through the entire subframe is to set a duration of each channel for transmitting a signal to the maximum extent possible in order to reduce instantaneous maximum power consumed by the UE.
However, there is a case where the RS cannot transmit or receive a signal through one entire subframe from the perspective of the time domain. In general, the RS relays a signal with respect to a plurality of UEs, which results in frequent occurrence of switching between a reception (Rx) mode and a transmission (Tx) mode. The switching between the Rx mode and the Tx mode requires a specific time (hereinafter referred to as a guard time) between an Rx-mode period and a Tx-mode period. During the guard time, the RS does not transmit or receive a signal in order to avoid inter-signal interference and to provide reliable operations.
Due to the guard time, the RS may not be able to transmit or receive a signal through the entire subframe unlike in the UE. In this case, the conventional method of transmitting a signal between the BS and the UE cannot be directly used.
In addition, the conventional method of transmitting a signal between the BS and the UE does not have to be directly used to transmit a signal between the BS and the RS in a sense that the RS is less restrictive in terms of power than the UE and that a channel state with respect to the BS is good in general.
Accordingly, there is a need for a new method of transmitting a signal in a wireless communication system employing an RS.